I hardly ever see WSMs on CL and when they do come up, they don't last long (unless they're priced at parity with new ones.
) Probably the same is true of the ceramic cookers though I have no direct experience with those. That's lkely to be the sweet spot for resale value.
Cheaper smokers (Char Broil, Char Griller) ECBs probably not so much. I see some that are regular residents on CL.
Once you get into the quality offsets and bigger smokers you have a smaller market. That makes it harder to get a good price though if you find a buyer who really wants what you have, they could get a decent return. Then again, maybe buyers in that market prefer to buy new and get exactly what they want. Again, I have no direct experience and I'm just speculating.
A UDS would be a special case. If you figure resale based on cost of materials, you could do well. If you factor in time and effort, you'll probably take a beating.